Recently, the demand for portable electronic products such as notebooks, video cameras, cellular phones or the like has rapidly increased, and electric vehicles, energy storage batteries, robots, satellites have been actively developed. For this reason, high-performance secondary batteries allowing repeated charging and discharging are being actively studied.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging or discharging, low self-discharging, and high energy density.
A lithium secondary battery generally uses lithium oxide and carbonaceous material as a positive electrode active material and negative electrode active material, respectively. The lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed between them, and an exterior, namely a battery case, which seals and accommodates the electrode assembly together with an electrolyte.
Generally, a lithium secondary battery may be classified into a can-type secondary battery where the electrode assembly is included in a metal can and a pouch-type battery where the electrode assembly is included in a pouch of an aluminum laminate sheet, depending on the shape of the exterior.
Recently, secondary batteries are widely used not only for small-sized devices such as cellular phones but also middle-sized or large-sized devices such as vehicles and power storages. In particular, along with the exhaustion of carbon energy and the increased interest on environments, hybrid electric vehicles and electric vehicles attract attention globally, for example in US, Europe, Japan and Korea. In such a hybrid electric vehicle or electric vehicle, a battery pack for giving a driving force to a vehicle motor is the most essential part. Since a hybrid electric vehicle or electric vehicle may obtain a driving force by means of charging and discharging of the battery pack, the hybrid electric vehicle or electric vehicle ensures excellent fuel efficiency and exhausts no or reduced pollutants, and for this reason, hybrid electric vehicles and electric vehicles are used more and more.
Generally, a battery pack is configured so that electronic components such as a cell assembly which is a secondary battery aggregation having at least one secondary battery, a battery management system (BMS), a current sensor, a relay, a fuse or the like are included in a housing. When configuring such a battery pack, it is very important how components of the battery pack such as a cell assembly are coupled in the housing.
Further, the battery pack may receive external physical forces such as vibrations and impacts. In particular, a battery pack mounted to an electric vehicle, including a hybrid vehicle, may be frequently exposed to vibrations and impacts due to the nature of the vehicle, and such vibrations and impacts are not weak. Therefore, in order to protect various components of the battery pack from being broken or damaged due to external physical forces, every components of the battery pack, such as a cell assembly, should be stably fixed in the housing without being moved.
However, in an existing battery pack, each component such as a cell assembly is not stably coupled in the housing. In particular, in case of an existing battery pack, a cell assembly is generally fixed in the housing by securing a lower or side surface of the cell assembly. However, if a side surface is fixed, the space for the fixation is required to some extent as a side of the cell assembly, and thus this configuration may not be easily applied to a battery pack having a narrow inner space, and even though this configuration is applied, the battery pack inevitably has an increased volume. In addition, if a lower surface is fixed, when an impact or the like is applied to the battery pack, the impact is focused on the fixation portion at the lower surface of the cell assembly, and thus the fixation portion may be easily broken, which can lead to breakage or damage of the cell assembly, and further the battery pack.